East Timor’s prime minister Xanana Gusmão has condemned Australia’s raid on the premises of a former spy and a lawyer acting for East Timor in a legal dispute with Australia.

Mr Gusmão said raiding the ­Canberra premises of a legal representative of Timor-Leste and taking such “aggressive action against a key ­witness is unconscionable and unacceptable conduct”.

“The actions taken by the Australian government are counterproductive and unco-operative,” he said in a statement issued on Wednesday.

He urged Prime Minister Tony Abbott to explain the government’s actions and “ensure the safety of our witness for a prompt, just and fair ­resolution of this important matter.”

Earlier, Australia’s Attorney-General George Brandis said the raid was to protect national security, not to subvert the legal claim.

The Australian Security Intelligence Organisation raids on Tuesday night targeted an unnamed former Australian Secret Intelligence Service (ASIS) employee, and lawyer Bernard Collaery, who is a former ACT ­attorney-general, and representing East Timor in a case that starts in The Hague on Thursday.

Separately, foreign minister Julie Bishop will travel to Indonesia, China and Philippines in a visit designed to smooth escalating tensions in the region over revelations that Australia spied on Indonesian President Susilo Bambang Yudhoyono, and over the ownership of the disputed Senkaku, or Diaoyu, islands.

East Timor has accused ASIS of secretly recording East Timorese ministers and officials during delicate oil and gas negotiations in Dili in 2004 relating to the Timor Sea resources treaty. It is pursuing arbitration in The Hague, in the Netherlands, to have the treaty overturned and claims the bugging was approved by former foreign minister Alexander Downer.

ASIO instructed not to share documents

Senator Brandis told the Senate he had not “set” ASIO on Mr Collaery or the ASIS whistle-blower, but rather that ASIO had sought a search warrant and he had approved it. He said he was not aware of what material had been identified by ASIO ahead of the raid, but he had been satisfied the request for documents had conformed to statutory tests.

“Last night, rather wild and inju­dicious claims were made by Mr Collaery and, disappointingly, Father Frank Brennan, that the purpose for which search warrants were issued was to somehow impede or subvert the arbitration. Those claims are wrong,” ­Senator Brandis said.

“The search warrants were issued, on the advice and at the request of ASIO, to protect Australia’s national security,” he said, adding that ASIO would not share information with Australia’s legal team in The Hague.

Mr Collaery said ASIO raided his home and office and seized documents to “muzzle” the ASIS whistle-blower. He said the former spy had direct ­knowledge of the operation to bug East Timorese politicians, but his passport had now been seized.

“This witness was the director of all technical operations at ASIS. We’re not talking about some disaffected spy,” Mr Collaery said.

Shorten seeks briefing

Earlier, East Timor’s ambassador to Australia Abel Guterres dismissed suggestions the absence of a key witness in The Hague could damage East Timor’s case.

“You can read it either way, it can be negative or positive. I suppose positive in the sense that if the key witness doesn’t appear, I’m sure the arbitrators would take that into account,” Mr Guterres said. “The arbitrators will come to their own conclusion.”

Mr Downer dismissed reports he ordered Australia’s external intel­ligence agency to spy on East Timor as an “old story”.

The 2006 Treaty on Certain Maritime Arrangements in the Timor Sea (CMATS) equally divides spoils from the vast oil and gas assets found in waters between the two countries.